<?xml version="1.0" encoding="utf-8"?>
 <grammar xmlns="http://relaxng.org/ns/structure/1.0">
   <start>
    <element name="library">
     <oneOrMore>
      <ref name="book-element"/>
     </oneOrMore>
    </element>
   </start>
 	<include href="included.rng"/>
   <define name="author-element">
    <element name="author">
     <attribute name="id"/>
     <ref name="name-element"/>
     <ref name="born-element"/>
     <optional>
      <ref name="dead-element"/>
     </optional>
    </element>
   </define>
   <define name="book-element">
    <element name="book">
     <attribute name="id"/>
     <attribute name="available"/>
     <ref name="isbn-element"/>
     <ref name="title-element"/>
     <zeroOrMore>
      <ref name="author-element"/>
     </zeroOrMore>
     <zeroOrMore>
      <ref name="character-element"/>
     </zeroOrMore>
    </element>
   </define>
   <define name="character-element">
    <element name="character">
     <attribute name="id"/>
     <ref name="name-element"/>
     <ref name="born-element"/>
     <ref name="qualification-element"/>
    </element>
   </define>
  </grammar>
